1. Field of the Disclosure
This disclosure relates to air filters and more generally to filtering devices for fluids. The disclosure addresses a filter assembly that has filter media that moves relative to the filter assembly.
2. Background
One application of a filter assembly that employs teachings from the present disclosure is in a filter assembly intended for placing in a return air duct for a heating, ventilation, and air conditioning system (HVAC system) or any air handling system that performs a subset of those functions. Filters are intended to be replaced or at least removed and cleaned from time to time in order to prevent accumulated particles on the upstream side of the filter from severely restricting the flow of air through the system or requiring unusual amount of energy to be provided to fans to provide a requisite amount of air flow. Restricting the airflow through the system may cause the air conditioning compressor to have to work longer in order to cool a building as the reduced air flow across the cooling coils causes the system to work slower than designed. Extending the compressor operating time increases the energy consumed in the cooling operation.
Frequently the duct has a flange near a grilled opening to the system. The duct flange extends outward to allow the perimeter of an air filter to rest against the duct flange on the upstream side so that the flow of air tends to push the air filter towards that duct flange rather than away from the duct flange. Thus, a prior art air filter was typically filter material surrounded by a frame that substantially filled the non-flanged portion of the duct and the downstream face of the frame fit against the upstream side of the duct flange. Frequently there is a standard depth for air filters so that the air filter fits entirely between two planes defined by the front of the duct and the duct flange.